Method to control battery cooling using the battery coolant pump in electrified vehicles

ABSTRACT

A climate-control system for a vehicle, comprising a controller in communication with a chiller configured to cool a vehicle battery and an evaporator configured to cool a vehicle cabin. The controller is configured to output a target chiller-pump speed based upon a difference between a battery coolant temperature and a target-battery coolant temperature to mitigate a temperature swing of air entering the cabin, and limiting the target chiller-pump speed in response to an available capacity of the chiller.

TECHNICAL FIELD

The present disclosure relates to a control strategy and method foroperating an evaporator associated with an air-conditioning system of avehicle.

BACKGROUND

The need to reduce fuel consumption and emissions in automobiles andother vehicles is well known. Vehicles are being developed that reducereliance or completely eliminate reliance on internal-combustionengines. Electric and hybrid vehicles are one type of vehicle currentlybeing developed for this purpose. Electric and hybrid vehicles include atraction motor that is powered by a traction battery. Traction batteriesrequire a thermal-management system to thermally regulate thetemperature of the battery cells. Such thermal-management systems mayalso be utilized to cool the vehicle's cabin.

SUMMARY

A first illustrative embodiment discloses a climate-control system for avehicle, comprising a controller in communication with a chillerconfigured to cool a vehicle battery and an evaporator configured tocool a vehicle cabin. The controller is configured to output a targetchiller- pump speed based upon a difference between a battery coolanttemperature and a target-battery coolant temperature to mitigate atemperature swing of air entering the cabin, and limiting the targetchiller-pump speed in response to an available capacity of the chiller.

A second illustrative embodiment discloses a climate-control system fora vehicle, comprising a chiller utilized to cool a battery in thevehicle, an evaporator utilized to cool a cabin in the vehicle, and avehicle controller. The vehicle controller is in communication with thechiller and evaporator, and configured to generate for output a targetchiller-pump speed of the chiller that corresponds to a differencebetween a temperature of the battery and a target temperature of thebattery to mitigate a temperature swing of air entering the cabin.

A third illustrative embodiment discloses a method of climate control ina vehicle, comprising cooling a battery and cabin of a vehicle at atarget chiller-pump speed of a chiller, the target speed correspondingto a difference between a temperature of an battery and a targettemperature of the battery, and wherein the target pump speed does notexceed a limit defined by a look-up table that identifies a capacity ofthe chiller by mapping the load and the difference.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an example electric vehicle.

FIG. 2 is a schematic diagram of a climate-control system of a vehicle.

FIG. 3 is a flow chart illustrating logic for controlling an airconditioning system.

FIG. 4 is flow chart illustrating logic for controlling a pump speed inan air conditioning system.

FIG. 5A is an exemplary chart that diagrams the chiller load as afunction of the blower speed and ambient air temperature

FIG. 5B is an exemplary chart that diagrams chiller availability as afunction of the chiller load and the evaporator error.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described herein. It is to beunderstood, however, that the disclosed embodiments are merely examplesand other embodiments can take various and alternative forms. Thefigures are not necessarily to scale; some features could be exaggeratedor minimized to show details of particular components. Therefore,specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a representative basis forteaching one skilled in the art to variously employ the presentinvention. As those of ordinary skill in the art will understand,various features illustrated and described with reference to any one ofthe figures can be combined with features illustrated in one or moreother figures to produce embodiments that are not explicitly illustratedor described. The combinations of features illustrated providerepresentative embodiments for typical applications. Variouscombinations and modifications of the features consistent with theteachings of this disclosure, however, could be desired for particularapplications or implementations.

FIG. 1 depicts a schematic of an example battery-electric vehicle (BEV).Certain embodiments, however, may also be implemented within the contextof hybrid-electric vehicles. The vehicle 12 includes one or moreelectric machines 14 mechanically connected to a transmission 16. Theelectric machines 14 may be capable of operating as a motor or agenerator. If the vehicle is a hybrid-electric vehicle, the transmission16 is mechanically connected to an engine (not shown). The transmission16 is mechanically connected to the wheels 22 via a driveshaft 20. Theelectric machines 14 can provide propulsion and deceleration capability.The electric machines 14 also act as generators and can provide fueleconomy benefits by recovering energy through regenerative braking.

A traction battery or battery pack 24 stores energy that can be used bythe electric machines 14. The traction battery 24 typically provides ahigh-voltage direct current (DC) output from one or more battery cellarrays, sometimes referred to as battery cell stacks, within thetraction battery 24. The battery cell arrays may include one or morebattery cells.

The battery cells (such as a prismatic, pouch, cylindrical, or any othertype of cell), convert stored chemical energy to electrical energy. Thecells may include a housing, a positive electrode (cathode) and anegative electrode (anode). An electrolyte may allow ions to movebetween the anode and cathode during discharge, and then return duringrecharge. Terminals may allow current to flow out of the cell for use bythe vehicle. Sensors may be utilized to determine a temperature of thevarious battery cells.

Different battery pack configurations are available to addressindividual vehicle variables including packaging constraints and powerrequirements. The battery cells may be thermally regulated with athermal management system. Examples of thermal management systemsinclude air-cooling systems, liquid-cooling systems, and a combinationof air and liquid systems.

The traction battery 24 may be electrically connected to one or morepower electronics modules 26 through one or more contactors (not shown).The one or more contactors isolate the traction battery 24 from othercomponents when opened, and connect the traction battery 24 to othercomponents when closed. The power-electronics module 26 may beelectrically connected to the electric machines 14 and may provide theability to bi-directionally transfer electrical energy between thetraction battery 24 and the electric machines 14. For example, a typicaltraction battery 24 may provide a DC voltage while the electric machines14 may require a three-phase alternating current (AC) voltage tofunction. The power-electronics module 26 may convert the DC voltage toa three-phase AC voltage as required by the electric machines 14. In aregenerative mode, the power-electronics module 26 may convert thethree-phase AC voltage from the electric machines 14 acting asgenerators to the DC voltage required by the traction battery 24.

In addition to providing energy for propulsion, the traction battery 24may provide energy for other vehicle electrical systems. A typicalsystem may include a DC/DC converter 28 that converts the high-voltageDC output of the traction battery 24 to a low-voltage DC supply that iscompatible with other vehicle components. Other high-voltage loads, suchas air-conditioning compressors and electric heaters, may be connecteddirectly to the high-voltage supply without the use of a DC/DC convertermodule 28. In a typical vehicle, the low-voltage systems areelectrically connected to the DC/DC converter and an auxiliary battery30 (e.g., a 12 volt battery).

A battery energy control module (BECM) 33 may be in communication withthe traction battery 24. The BECM 33 may act as a controller for thetraction battery 24 and may also include an electronic monitoring systemthat manages temperature and state of charge for each of the batterycells. The traction battery 24 may have a temperature sensor 31 such asa thermistor or other temperature gauge. The temperature sensor 31 maybe in communication with the BECM 33 to provide temperature dataregarding the traction battery 24. The BECM 33 may be part of a largervehicle-control system that includes one or more additional controllers.

The vehicle 12 may be recharged by an external power source 36. Theexternal power source 36 may be a connection to an electrical outletconnected to the power grid or may be a local power source (e.g. solarpower). The external power source 36 is electrically connected to avehicle charging station 38. The charger 38 may provide circuitry andcontrols to regulate and manage the transfer of electrical energybetween the power source 36 and the vehicle 12. The external powersource 36 may provide DC or AC power to the charger 38. The charger 38may have a charge connector 40 for plugging into a charge port 34 of thevehicle 12. The charge port 34 may be any type of port configured totransfer power from the charger 38 to the vehicle 12. The charge port 34may be electrically connected to a charger or on-board power-conversionmodule 32. The power- conversion module 32 may condition the powersupplied from the charger 38 to provide the proper voltage and currentlevels to the traction battery 24. The power-conversion module 32 mayinterface with the charger 38 to coordinate the delivery of power to thevehicle 12. The charger connector 40 may have pins that mate withcorresponding recesses of the charge port 34. In other embodiments, thecharging station may be an induction charging station. Here, the vehiclemay include a receiver that communicates with a transmitter of thecharging station to wirelessly receive electric current.

The various components discussed may have one or more controllers tocontrol and monitor the operation of the components. The controllers maycommunicate via a serial bus (e.g., Controller Area Network (CAN)) orvia dedicated electrical conduits. The controller generally includes anynumber of microprocessors, ASICs, ICs, memory (e.g., FLASH, ROM, RAM,EPROM and/or EEPROM) and software code to co-act with one another toperform a series of operations. The controller also includespredetermined data, or “look up tables” that are based on calculationsand test data, and are stored within the memory. The controller maycommunicate with other vehicle systems and controllers over one or morewired or wireless vehicle connections using common bus protocols (e.g.,CAN and LIN). Used herein, a reference to “a controller” refers to oneor more controllers.

The traction battery 24, the passenger cabin, and other vehiclecomponents are thermally regulated with one or more thermal-managementsystems. Example thermal-management systems are shown in the figures anddescribed below. Referring to FIG. 2, the vehicle 12 includes aclimate-control system 50 having at least a refrigerant subsystem 52 andbattery-coolant subsystem 54. Portions of the various thermal-managementsystems may be located within various areas of the vehicle, such as theengine compartment and the cabin, for example.

The refrigerant subsystem 52 provides air conditioning of the cabinduring some operating modes, and also cools the battery 24 during someoperating modes. The refrigerant subsystem 52 may be a vapor-compressionheat pump that circulates a refrigerant transferring thermal energy tovarious components of the climate-control system 50. The refrigerantsubsystem 52 may include a cabin loop 56 having a compressor 57, anexterior heat exchanger 58 (e.g., condenser), a first interior heatexchanger 60 (e.g., front evaporator), a second interior heat exchanger62 (e.g., rear evaporator), an accumulator, fittings, valves, expansiondevices and other components commonly associated with refrigerantsubsystems. The evaporators may each have an associated blower 61. Thecondenser 58 may be located behind the grille near the front of thevehicle, and the evaporators may be disposed within one or more HVAChousings. It is to be understood that heat exchangers labeled as“condenser” may also act as an evaporator if the refrigerant subsystem52 is a heat pump. A fan 59 may circulate air over the condenser 58. Ahigh-side-pressure transducer 65 may be located between the A/Ccompressor and the condenser in conduit 64.

The cabin loop 56 components are connected in a closed loop by aplurality of conduits, tubes, hoses or lines. For example, a firstconduit 64 connects the compressor 57 and the condenser 58 in fluidcommunication, a second conduit 66 connects the condenser 58 to theintermediate heat exchanger 82, and conduit 67 connects the evaporators60 and 62 in fluid communication with the heat exchanger 82. The frontevaporator 60 is connected with conduit 67 via conduit 68, and the rearevaporator 62 is connected with conduit 67 via conduit 70. A firstexpansion device 78 is disposed on conduit 68 and controls refrigerantflow to the front evaporator 60. The expansion device is configured tochange the pressure and temperature of the refrigerant in the subsystem52. The expansion device 78 may be a thermal expansion valve with anelectronically controllable shut-off feature or may be an electronicexpansion valve. A second expansion device 80 is disposed on conduit 70and controls refrigerant flow to the rear evaporator 62. The secondexpansion device 80 may be similar to the first expansion device. Thefront evaporator 60 is connected to a return conduit 76 via conduit 74,and the rear evaporator 62 is connected with return conduit 76 viaconduit 72. The return conduit 76 connects between the heat exchanger 82and the evaporators. Conduit 77 connects between the heat exchanger 82and the compressor 57. The intermediate heat exchanger 82 is optional.

The climate-control system 50 includes a controller 100 in electroniccommunication with several of the climate-control components. The dashedlines in FIG. 2 illustrate electrical connections between the controller100 and the components. The controller may interface with the variouscomponents via a data bus or dedicated wires as described above. Theevaporators 60 and 62 each include a temperature sensor 84 and 86,respectively, that is configured to send a signal indicating thetemperature of the corresponding evaporator to the controller 100. Usingthese temperature signals, and other signals, the controller 100 candetermine the operating conditions of the climate-control system 50.

The refrigerant subsystem 52 also includes a chiller refrigerant line 89having a chiller 90 and a third expansion device 92. The chillerrefrigerant line 89 may include a supply conduit 94 connected to conduit66 at fitting 96 and connected to the refrigerant-inlet side 101 of thechiller 90. The third expansion device 92 may be similar to the firstexpansion device 78 described above. A return conduit 98 may beconnected to the battery chiller 90 and to return conduit 77. The returnconduit 98 is connected to the refrigerant-outlet side 102 of thechiller at one end and is connect with conduit 77 at the other end.Optionally, the return conduit 98 may be connected to the batterychiller 90 and to the cabin loop 56 via conduit 76, which is not shownin FIG. 2.

The vehicle also includes a battery thermal-management system thatoperates in a plurality of different modes, such as battery-heating modeor battery-cooling mode. The battery thermal-management system includesa battery-coolant subsystem 54 (shown) that dissipates heat to therefrigerant subsystem 52 via the chiller 90, and a radiator loop (notshown) that dissipates heat to the ambient air via a radiator. These twoloops may operate in tandem or independently of each other dependingupon the battery cooling requirements, the ambient air temperature, andother factors.

The battery-coolant subsystem 54 connects the traction battery 24 or (abattery cold plate) and the chiller 90 in fluid communication. Thesubsystem 54 includes a chiller pump 104 disposed on a first conduit 106that connects between the battery 24 and the coolant-inlet side 114 ofthe chiller 90. A second conduit 108 connects between the coolant-outletside 116 and the battery 24.

A coolant inlet temperature sensor 110 is disposed on conduit 106 nearthe inlet side 114. The sensor 110 is configured to output a signal tothe controller 100 indicating a temperature of the coolant circulatinginto the chiller 90. A coolant outlet temperature sensor 112 is disposedon conduit 108 near the outlet side 116. The sensor 112 is configured tooutput a signal to the controller 100 indicating a temperature of thecoolant exiting the chiller 90 and entering the battery 24.

The battery chiller 90 may have any suitable configuration. For example,the chiller 90 may have a plate-fin, tube-fin, or tube-and-shellconfiguration that facilitates the transfer of thermal energy withoutmixing the heat-transfer fluids in the coolant subsystem 54 and therefrigerant subsystem 52.

In systems in which the battery chiller is in fluid communication with acabin AC system (such as refrigerant subsystem 52), a potential fornegatively affecting the temperature of the cabin air is possible if theAC system does not have enough capacity to cool both the cabin and thebattery at their respective loads. For example, on a hot day,simultaneously cooling the battery and the passenger cabin via the ACsystem may cause the outlet temperature of the cabin evaporator toincrease beyond a target temperature, which causes the air blowing intothe cabin to be warmer than that requested by the driver. The occupantsof the cabin may find it dissatisfying when the cabin temperature is notconforming with the demanded temperature. As such, the vehicle may berequired to choose between satisfying cabin demands versus satisfyingbattery demands in situations in which the combined load exceeds thecapacity.

In one embodiment, the system may be designed to balance the cabindemand and the battery demand. Based upon the conditions of the ACsystem 52, the pump 104 speed and therefore coolant flow through thechiller may be controlled to meet demands of first the cabin whilemanaging the left over AC capacity for the battery chiller.Additionally, the controller may be configured to determine a capacity(e.g. “chiller capacity”), of the refrigerant system to acceptadditional heat and based on the chiller capacity, route an appropriateamount of coolant to the chiller and therefore increasing therefrigerant through the chiller 90 in order to provide that capacity. Inthe illustrated embodiment, the chiller pump 104 speed translates tocoolant flow through the chiller and may be used to control thepercentage of refrigerant flowing to the chiller 90 versus thepercentage of refrigerant bypassing the chiller via conduits 68 or 70.Depending upon the conditions of the cabin AC system 52, the pump speedmay controlled to send between zero and 100 percent of the coolant tothe chiller. Additionally in another embodiment, if no chiller capacityis available, the battery-coolant system may attempt to cool the batteryusing a radiator in conjunction with a fan. In some instances, theradiator and fan may be unable to achieve a sufficiently low batterycoolant temperature for a given battery load. To prevent overheating,the controller may power limit the battery to prevent overheating.

Control logic or functions performed by controller 100 may berepresented by flow charts or similar diagrams in one or more figures.These figures provide representative control strategies and/or logicthat may be implemented using one or more processing strategies such asevent-driven, interrupt-driven, multi-tasking, multi-threading, and thelike. As such, various steps or functions illustrated may be performedin the sequence illustrated, in parallel, or in some cases omitted.Although not always explicitly illustrated, one of ordinary skill in theart will recognize that one or more of the illustrated steps orfunctions may be repeatedly performed depending upon the particularprocessing strategy being used. Similarly, the order of processing isnot necessarily required to achieve the features and advantagesdescribed herein, but is provided for ease of illustration anddescription. The control logic may be implemented primarily in softwareexecuted by a microprocessor-based vehicle, engine, and/or powertraincontroller, such as controller 100. Of course, the control logic may beimplemented in software, hardware, or a combination of software andhardware in one or more controllers depending upon the particularapplication. When implemented in software, the control logic may beprovided in one or more computer-readable storage devices or mediahaving stored data representing code or instructions executed by acomputer to control the vehicle or its subsystems. The computer-readablestorage devices or media may include one or more of a number of knownphysical devices which utilize electric, magnetic, and/or opticalstorage to keep executable instructions and associated calibrationinformation, operating variables, and the like.

FIG. 3 is a flow chart 300 illustrating logic for controlling an airconditioning system. The controller may first begin by determiningwhether an incoming request for the chiller has been received at 301. Ifthe chiller has not been requested, there may be no need to determinethe chiller capacity and the pump speed is determined based on thebattery needs and battery cooling loop. However, if the chiller has beenrequested, it may be required to determine if the cabin is also beingcooled at 303.

In the scenario that the cabin is not being cooled, the battery may be acomponent that needs to be cooled at 305. The battery may be cooled byutilizing the chiller of the battery-coolant system. As such, the pumpmay be run at full speed through the chiller at step 307. As such, thecompressor speed may be defined in response to the battery coolanttemperature error at 309. The battery coolant temperature error may bethe difference between the target battery inlet coolant temperature andthe actual battery inlet coolant temperature. Such a difference may beutilized when the chiller is in use to determine if the battery coolingneeds are met, and the cabin is not being cooled (e.g. by theevaporator). The compressor speed may be determined utilizing aproportion integration (PI) controller that utilizes the differencebetween the target battery inlet coolant temperature and the actualbattery inlet coolant temperature.

In a scenario when the cabin is being cooled, a controller may determinethe evaporator error by calculating the difference between the targetevaporator temperature and the actual evaporator temperature at step311. The controller may calculate a target evaporator temperature byutilizing various inputs, such as the cabin set point (e.g. temperatureset point set by the customer), the cabin temperature, the ambienttemperature, the solar load, and other operating conditions.

At step 313, a controller may determine the cabin thermal load, forexample, utilizing the table mapped in FIG. 5A. As described below, thecabin thermal load is a function of the blower speed and the ambient-airtemperature. The controller may be configured to determine a totalcapacity of the AC system, the amount of the total capacity being usedby the cabin evaporator (which may be called evaporator capacity), and achiller capacity that is available to the chiller if needed. The chillercapacity is the reserve capacity of the refrigerant system to acceptadditional heat from the chiller. The chiller capacity may be equal tothe total system capacity minus the evaporator capacity. The controllermay be programmed to determine the chiller capacity as a function of thecabin thermal load, and a temperature differential between a targetevaporator temperature and a measured evaporator temperature. The targettemperature of an evaporator is based on the cabin temperature requestedby the driver, ambient-air temperature, sun load, and climate-controlmode.

For example, if the driver requests a 21 degrees Celsius cabintemperature, the controller may include mapping indicating a targetevaporator temperature of 2-9 degrees Celsius range with 6 degrees beinga typical target evaporator value. The cabin thermal load is a functionof the temperature of the ambient air and the speed of the cabin blowerthat circulates air over the evaporator. An example high load occurswhen the blower is on HIGH and the ambient air is above 30 degreesCelsius, and an example low load occurs when the blower is on LOW andthe ambient air is below 20 degrees Celsius. The thermal load could alsotake into account ambient air temperature, sun load, cabin temperatureset point, sun load, and the number of vehicle occupants. Ambient airtemperature may reference the intake air temperature into the HVACsystem. Additionally, this intake air could be directly from outside thevehicle, or ambient air, or from the cabin in a full recirculationsetting, partial recirculation setting, or a combination of both. In analternative embodiment, the thermal load may take into account atemperature from an inlet air temperature sensor.

At step 315, the air conditioning's capacity available to the chillermay be determined. The air condition's chiller availability may bedetermined utilizing a look-up table that maps the chiller capacity as afunction of the cabin thermal load and the evaporator error. The chillerair conditioning capacity may be a function between the cabin thermalload calculated at step 313 and the evaporator error calculated at 311.The controller may also determine if the chiller capacity is greaterthan zero. If the chiller capacity is zero, the chiller may not be usedto cool the battery. As such, the control loops back to the start. Ifthe chiller capacity is greater than zero, control passes to operation317 and the controller translates the chiller capacity to a maximum pumpspeed. The controller may begin to cool the cabin and battery at step317. The controller may initially calculate the pump speed at step 319,and output the target pump speed. The pump speed may be calculatedutilizing factors such as the battery coolant temperature and the targetbattery coolant temperature. Furthermore, a limit may be set on themaximum pump speed based on the capacity of the chiller. As described inadditional detail with respect to FIG. 4, the target pump speed may bedetermined utilizing several factors.

At operation 321, a controller may determine the temperature of theindividual cells in a battery. Sensors within the battery may beutilized to determine the temperature of each battery cell and thosesensors may be in communication with one or more controllers. Each cellsindividual temperature may be utilized to determine the change intemperature across cells in the battery. The controller may beprogrammed to include a defined threshold to determine a change intemperature. The controller may be utilized to determine if a changebetween battery cell temperatures falls above the threshold value. Atemperature change between battery cells may grow apart and the gradienttemperature of the battery may grow too large. Such an increase in thebattery cell temperature may require full coolant flow to coolof thebattery to avoid temperature swings. This may require the vehicle'sthermal management system to prioritize cooling the battery, as opposedto a steady ramp up of the battery cooling to prevent discharge airtemperature swings to the cabin. If the battery temperature ishomogeneous or cell to cell temps are below the threshold, then thevehicle's thermal management system may ramp-up cooling efforts to thebattery. This may be beneficial to avoid large temperature swings to thecabin. If the change in the battery's cell temperature is above athreshold, the pump can run at a maximum speed at operation 323 or at amaximum speed as defined by the capacity of the chiller. This logic mayprevent large gradients of the battery to promote durability of thebattery.

At operation 327, the controller may utilize a look-up table to ramp upthe target speed of the pump as a function of the chiller capacity overtime. The look-up table may be defined in a manner to mitigatetemperature swings of cooling efforts in the cabin. The ramp-up speedmay be allocated over time as a function of coolant temperature measuredby a sensor in the chiller inlet sensor 110. In another embodiment, theramp-up speed may be over time as a function of coolant temperaturemeasured by sensor 112 with an offset if the chiller inlet sensor 112 isunavailable. This may help mitigate influence on the cabin air swings ata set pump ramp rate. For instance, the pump flow rate may be defined tomanage capacity of the chiller to allow the refrigerant system torespond to temperature demands between the battery and cabin. In otherwords, the pump speed ramp rate or speed at which the pump will go fromzero to the target speed is a function of how hot the coolanttemperature is. For example, if the coolant is at 50 degrees Celsius,the pump may take ten seconds to reach the target speed. But if thecoolant is at 30 degrees Celsius then the pump may take five seconds toreach the target speed.

At operation 329, the compressor speed may be defined in response tocalculating the difference between the target evaporator temperature andthe actual evaporator temperature. The evaporator error or thedifference between evap. target and actual is at its maximum when thecabin is first requested to cool, and the overall cabin cool down may byextended if the chiller is also running. The compressor speed may bedetermined utilizing a proportion integration (PI) controller thatutilizes the difference between the target evaporator temperature andthe actual evaporator temperature when the cabin is requested in eithera “cabin only” circumstance or when the cabin and chiller aresimultaneously running. The compressor speed PI controller in chilleronly mode is determined based on battery coolant error which is thedifference between battery chiller target and actual battery coolanttemperature as measure by sensor 112. Additionally, the refrigerantvalves 78, 80, and 92 are actuated to open or close depending on themode. For example, the controller may open valves 78 or 80 when thefront or rear cabin are on and close 92 if the chiller is not requested.The controller may open 92 when the chiller is running. Also during achiller only mode, valves 78 and 80 may be closed, while shutoff andexpansion valve 92 may be open to allow refrigerant flow to the chiller.Chiller only controls may run the chiller pump 104 at full speed and thecompressor speed is determined based on battery coolant error. When thecabin is also running, the battery or chiller capacity may be controlledusing the chiller pump 104.

FIG. 4 shows a flow chart illustrating logic for controlling a chillerpump 104 speed in an air conditioning system. At operation 401, thebattery temperature controller may receive information from sensors todetermine a temperature of the battery coolant at operation 403.Additionally, the controller may also define a target battery coolanttemperature at operation 404 based on a look-up table defining an idealtemperature for the battery coolant to be at in order for the airconditioning system to cool both the cabin and the battery. At operation405, the controller may define an error by determining the differencebetween the actual temperature and the target temperature of the batterycoolant temperature.

At operation 407, a PI controller may receive the error for the batterycoolant temperature. At operation 409, the PI controller may utilize theerror to generate for output an ideal pump speed or adjust the pumpspeed. A look-up table or the like may be utilized to map the pump speedadjustment to the error of the battery coolant temperature. While a pumpspeed may be desired, it may not always be possible or beneficial toutilize that pump speed based on the capacity of the chiller. Atoperation 411, the maximum pump speed may be adjusted or lowered basedon the capacity of the chiller, and a controller may define a clip orlimit to set the pump speed based on the capacity of the chiller.

While settings may be determined by various capacity levels of thechiller, in one embodiment the capacity may have several differentsettings. The settings may be utilized to translate chiller capacity toa pump speed. For example, chiller capacities categorized as “one” maycorrespond to a pump speed that routes 25% of the coolant to thechiller. In another example, if the chiller capacity is defined at aminimum level (e.g. level “one”), the coolant pump may be run atapproximately 25% of the ideal speed. In another example, if the chillercapacity is defined at a reduced level (e.g. level “two”), which may begreater than the minimum level, but less than full, the coolant pump maybe run at approximately 50% of the ideal speed. In another embodiment,if the chiller capacity is full, or at a level above the reduced level,the chiller capacity may be more than enough to cool the battery androuting too much coolant through the chiller may overcool the battery.Thus, the temperature controller will take over and the max clip on box411 will not be used but the temperature controller will define andideal pump speed to match the battery needs. The coolant pump speed maybe controlled based on a difference between a target battery inletcoolant temperature and a measured battery inlet coolant temperature.Such pump speed and settings are merely examples and are not limiting.

FIG. 5A is an exemplary chart that diagrams the cabin load as a functionof the blower speed and ambient air temperature. While the followingchart is exemplary, the chart demonstrates that the cabin load may varyas the blower speed percentage differs in comparison to the ambient airtemperature. For example, as blower speed temperature increases andambient air temperature increases, the cabin load value may increase.The load table may be stored in memory of the controller. The controllermay include one or more load tables that are selectively used duringdifferent operating conditions. In the table, the load increases withincreasing air temperatures and with increasing blower speeds. Theblower speed may be represented as a percentage.

FIG. 5B is an exemplary chart that diagrams chiller availability as afunction of the cabin load and the cabin evaporator error (e.g. thedifference between the actual evaporator temperature and the targetevaporator temperature). As shown by FIG. 5B, the load and evaporatorerror may have an impact as to the capacity of the chiller. In oneexample, the chiller may not be available if the evaporator error is atover 3 degrees C. In another example, the chiller may need to operate ata minimum chiller and therefore minimum pump speed dependent on theevaporator error, 2 degrees C., at different cabin loads. The chillermay also be full as shown on the left-hand side of the graph, forexample, when the evaporator error is 0.5. Finally, the chiller may bereduced in another scenario. While the graph contemplates fourscenarios/settings for the chiller, there may be additional or reducedscenarios/settings that may be defined as a function of the load andevaporator error. For instance, if the evaporator error is equal tozero, the cabin may be cooled. If the evaporator error is large (e.g.greater evaporator than three degrees), the cabin may not be cooled atthe desired rate, or the discharge of air temperatures may be high. Theair discharge that flows into the cabin may be directly proportional tothe temperature on the evaporator. Thus any evaporator temperatureswings may lead to cabin discharge air temperature swings. Thus, ideallyit may be beneficial to provide capacity to the chiller when theevaporator error is close to zero or below zero. As the evaporator errorgrows positive, the chiller capacity may need to be reduced so that theair discharged into the cabin is not raised.

What is claimed is:
 1. A climate-control system for a vehicle,comprising: a controller in communication with a chiller configured tocool a vehicle battery and an evaporator configured to cool a vehiclecabin, the controller configured to output a target chiller-pump speedbased upon a difference between a battery coolant temperature and atarget-battery coolant temperature to mitigate a temperature swing ofair entering the cabin, and limiting the target chiller-pump speed inresponse to an available capacity of the chiller.
 2. The climate-controlsystem of claim 1, wherein a pump speed is adjusted in response to thecapacity of the chiller.
 3. The climate-control system of claim 2,wherein the capacity of the chiller is defined utilizing a look-up tablemapping a cabin thermal load of the vehicle and a difference between anevaporator temperature and a target- evaporator temperature.
 4. Theclimate-control system of claim 2, wherein the pump speed is determinedsuch that coolant is increased in circulation to a chiller outlet ascapacity of the chiller increases.
 5. The climate-control system ofclaim 4, wherein the pump speed includes a first speed configured tooutput coolant at a first speed in response to the capacity of thechiller being full.
 6. The climate-control system of claim 4, whereinthe pump speed includes a second speed configured to output coolant at asecond speed being lower than a first speed in response to the chillercapacity being less than full.
 7. The climate-control system of claim 1,wherein the controller is further configured to determine a change intemperature of cells in the vehicle battery.
 8. The climate-controlsystem of claim 7, wherein the controller is further configured todefine a target pump speed in response to the change in temperature ofcells in the vehicle battery being below a temperature gradientthreshold value defining a temperature gradient in the vehicle battery.9. The climate-control system of claim 7, wherein the controller isfurther configured to output a maximum target speed in response to thechange in temperature of cells in the vehicle battery being above atemperature gradient value defining a temperature gradient in thevehicle battery.
 10. A climate-control system for a vehicle, comprising:a chiller utilized to cool a battery in the vehicle; an evaporatorutilized to cool a cabin in the vehicle; and a vehicle controller incommunication with the chiller and evaporator, configured to generatefor output a target chiller-pump speed of the chiller that correspondsto a difference between a temperature of the battery and a targettemperature of the battery to mitigate a temperature swing of airentering the cabin.
 11. The climate-control system of claim 10, whereinthe controller is configured to define the target chiller-pump speedusing a look-up table that maps the target chiller-pump speed to thedifference.
 12. The climate-control system of claim 10, wherein thecontroller is further configured to generate for output the targetchiller-pump speed in response to a capacity of the chiller.
 13. Theclimate-control system of claim 12, wherein the capacity of the chilleris defined by a look-up table mapping a cabin thermal load and thedifference between a temperature of the evaporator and a targettemperature of the evaporator.
 14. The climate-control system of claim10, wherein the vehicle controller is further configured to ramp to thetarget chiller-pump speed utilizing a look-up table mapping a capacityof the chiller and time to reach the target chiller-pump speed.
 15. Theclimate-control system of claim 10, wherein the controller is furtherconfigured to define the target chiller-pump speed in response to abattery's cell-to-cell temperature distribution exceeding a cell-to-celltemperature threshold.
 16. The climate-control system of claim 10,wherein the controller is further configured to define a limit of thetarget chiller-pump speed in response to a capacity of the chiller beingbelow a chiller-capacity threshold to reach the target pump speed. 17.The climate-control system of claim 16, wherein the limit lowers thetarget chiller-pump speed to a first threshold percentage in response tothe capacity being at a first level.
 18. The climate-control system ofclaim 16, wherein the limit lowers the target chiller-pump speed to asecond threshold percentage that is greater than a first thresholdpercentage in response to the capacity being at a second level that isgreater than a first level.
 19. The climate-control system of claim 16,wherein the limit does not lower the target chiller-pump speed inresponse to the capacity being greater than a first level and a secondlevel.
 20. A method of climate control in a vehicle, comprising: coolinga battery and cabin of a vehicle at a target chiller-pump speed of achiller, the target speed corresponding to a difference between atemperature of an battery and a target temperature of the battery, andwherein the target pump speed does not exceed a limit defined by alook-up table that identifies a capacity of the chiller by mapping theload and the difference.